Surgical patient side cart with drive system and method of moving a patient side cart

ABSTRACT

A cart for supporting one or more instruments for a computer-assisted, remote procedure can include a base and a support structure extending from the base and adjustable to different configurations, the support structure being configured to support one or more instruments to perform a remote procedure. The cart can further include a steering interface configured to be grasped by a user and a sensor mechanism configured to detect a force applied to the steering interface. The cart also can include a drive system comprising a control module operably coupled to receive an input from the sensor mechanism in response to the force applied to the steering interface and information about a configuration of the support structure, the control module operably coupled to output a movement command based on the received input from the sensor mechanism and the information about the configuration of the support structure. A driven wheel may be mounted to the base and configured to impart wheeled motion to the cart in response to the movement command.

This application is a continuation of U.S. application Ser. No.14/808,639 (filed Jul. 24, 2015), which is a continuation of U.S.application Ser. No. 14/209,239 (filed Mar. 13, 2014), now U.S. Pat. No.9,101,348, which claims the benefit of U.S. Provisional Application No.61/895,249, (filed Oct. 24, 2013), and U.S. Provisional Application No.61/791,889, (filed Mar. 15, 2013), each of which is incorporated byreference herein in its entirety.

TECHNICAL FIELD

Aspects of the present disclosure relate to a teleoperated (robotic)surgical system patient side cart having a drive system for a user tomaneuver the cart and methods of moving a patient side cart.

INTRODUCTION

The section headings used herein are for organizational purposes onlyand are not to be construed as limiting the subject matter described inany way.

Some minimally invasive surgical techniques are performed remotelythrough the use of teleoperated (robotically-controlled) surgicalinstruments. In teleoperated (robotically-controlled) surgical systems,surgeons manipulate input devices at a surgeon console, and those inputsare passed to a patient side cart that interfaces with one or moreteleoperated surgical instruments. Based on the surgeon's inputs at thesurgeon console, the one or more teleoperated surgical instruments areactuated at the patient side cart to operate on the patient, therebycreating a master-slave control relationship between the surgeon consoleand the surgical instrument(s) at the patient side cart.

A patient side cart need not remain stationary in a particular location,such as within one operating room, but instead may be moved from onelocation to another. For example, a patient side cart may be moved fromone location to another, such as from one location in an operating roomto another location in the same operating room. In another example, apatient side cart may be moved from one operating room to anotheroperating room.

One consideration in moving a patient side cart of a teleoperatedsurgical system is the ease with which the patient side cart may bemoved by a user. Due to its weight, size, and overall configuration, itmay be desirable to provide a patient side cart that enables a user tomove and maneuver the patient side cart with relative ease. It mayfurther be desirable to configure a patient side cart that can be movedfrom one location to another in a safe manner.

SUMMARY

Exemplary embodiments of the present disclosure may solve one or more ofthe above-mentioned problems and/or may demonstrate one or more of theabove-mentioned desirable features. Other features and/or advantages maybecome apparent from the description that follows.

In accordance with at least one exemplary embodiment, a patient sidecart for a teleoperated system comprises at least one manipulator armportion for holding a surgical instrument, a steering interface, and adrive system. The steering interface may be configured to detect a forceapplied by a user to the steering interface indicating a desiredmovement for the teleoperated surgical system. The drive system maycomprise at least one driven wheel, a control module, and a modelsection. The control module may receive as input a signal from thesteering interface corresponding to the force applied by the user to thesteering interface. The control module may be configured to output adesired movement signal corresponding to the signal received from thesteering interface. The model section may comprise a model of movementbehavior of the patient side cart, the model section outputting amovement command output to drive the driven wheel.

In accordance with at least one exemplary embodiment, a method of movinga patient side cart of a teleoperated surgical system, the patient sidecart including a steering interface and a surgical instrument comprisesthe steps of: detecting a force applied to the steering interface with asensor of the steering interface, transmitting an input corresponding tothe applied force from the steering interface sensor to a drive systemof the patient side cart, transmitting a desired movement command outputbased on the input corresponding to the applied force that is receivedfrom the steering interface, and transmitting a movement command outputbased on the desired movement signal and a modeled behavior of thepatient side cart.

Additional objects, features, and/or advantages will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the present disclosureand/or claims. At least some of these objects and advantages may berealized and attained by the elements and combinations particularlypointed out in the appended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the claims; rather the claims should beentitled to their full breadth of scope, including equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure can be understood from the following detaileddescription, either alone or together with the accompanying drawings.The drawings are included to provide a further understanding of thepresent disclosure, and are incorporated in and constitute a part ofthis specification. The drawings illustrate one or more exemplaryembodiments of the present teachings and together with the descriptionserve to explain certain principles and operation. In the drawings,

FIG. 1 is a diagrammatic view of an exemplary teleoperated surgicalsystem in accordance with at least one exemplary embodiment;

FIG. 2 is a schematic perspective view of an exemplary embodiment of apatient side cart that includes a steering interface;

FIG. 3 is a plan schematic view of an exemplary embodiment of a wheelarrangement of a patient side cart with a steering interface;

FIG. 4 is schematic top view of an exemplary embodiment of a patientside cart in a stowed configuration;

FIG. 5 is a schematic block diagram of an exemplary embodiment of adrive system for a patient side cart;

FIG. 6 is a schematic block diagram of an exemplary embodiment of acontrol system of a drive system for a patient side cart;

FIG. 7 is a schematic block diagram of an exemplary embodiment of acontrol system for a patient side cart that includes feedback control;

FIG. 8 is a schematic block diagram of another exemplary embodiment of acontrol system for a patient side cart that includes feedback control;and

FIG. 9 is a plan schematic view of an exemplary embodiment of a wheelarrangement of a patient side cart.

DETAILED DESCRIPTION

This description and the accompanying drawings that illustrate exemplaryembodiments should not be taken as limiting. Various mechanical,compositional, structural, electrical, and operational changes may bemade without departing from the scope of this description and theinvention as claimed, including equivalents. In some instances,well-known structures and techniques have not been shown or described indetail so as not to obscure the disclosure. Like numbers in two or morefigures represent the same or similar elements. Furthermore, elementsand their associated features that are described in detail withreference to one embodiment may, whenever practical, be included inother embodiments in which they are not specifically shown or described.For example, if an element is described in detail with reference to oneembodiment and is not described with reference to a second embodiment,the element may nevertheless be claimed as included in the secondembodiment.

For the purposes of this specification and appended claims, unlessotherwise indicated, all numbers expressing quantities, percentages, orproportions, and other numerical values used in the specification andclaims, are to be understood as being modified in all instances by theterm “about,” to the extent they are not already so modified.Accordingly, unless indicated to the contrary, the numerical parametersset forth in the following specification and attached claims areapproximations that may vary depending upon the desired propertiessought to be obtained. At the very least, and not as an attempt to limitthe application of the doctrine of equivalents to the scope of theclaims, each numerical parameter should at least be construed in lightof the number of reported significant digits and by applying ordinaryrounding techniques.

It is noted that, as used in this specification and the appended claims,the singular forms “a,” “an,” and “the,” and any singular use of anyword, include plural referents unless expressly and unequivocallylimited to one referent. As used herein, the term “include” and itsgrammatical variants are intended to be non-limiting, such thatrecitation of items in a list is not to the exclusion of other likeitems that can be substituted or added to the listed items.

Further, this description's terminology is not intended to limit theinvention. For example, spatially relative terms—such as “beneath”,“below”, “lower”, “above”, “upper”, “proximal”, “distal”, and thelike—may be used to describe one element's or feature's relationship toanother element or feature as illustrated in the figures. Thesespatially relative terms are intended to encompass different positions(i.e., locations) and orientations (i.e., rotational placements) of adevice in use or operation in addition to the position and orientationshown in the figures. For example, if a device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be “above” or “over” the other elements or features.Thus, the exemplary term “below” can encompass both positions andorientations of above and below. A device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

Various exemplary embodiments of the present disclosure contemplate acart with a drive system and methods of moving a cart. Such a cart maybe, for example, patient side cart of a teleoperated surgical systemthat includes a drive system. The drive system may include, for example,a control system that includes an inverse model of cart behavior.Further, the control system may include error correction, such as, forexample, feedback control. The features of the exemplary embodimentsdescribed herein may be applied to other wheeled objects, such as, forexample, imaging equipment, operating tables, and other wheeled devices.

A patient side cart of a teleoperated surgical system need not remainstationary in a particular location, such as within one operating room,but instead may be moved from one location to another. For example, apatient side cart may be moved from one location to another, such asfrom one location in an operating room to another location in the sameoperating room. In another example, a patient side cart may be movedfrom one operating room to another operating room.

Due to its size and the equipment and instrument that it may include, apatient side cart may have a considerable mass. For instance, a patientside cart may weigh from about 1000 pounds to about 2000 pounds, forexample. In another example, an exemplary patient side cart may have aweight ranging from about 1200 pounds to about 1850 pounds. Furthermore,a patient side cart may be large in size. If a person were required tosupply the force required to move a patient side cart, it may bedifficult for the person to also steering the cart while providing thenecessary motive force. Therefore, due to its weight, size, and overallconfiguration, it may be desirable to provide a patient side cart thatenables a user to move and maneuver the patient side cart with relativeease. It may further be desirable to configure a patient side cart thatcan be moved from one location to another in a safe manner.

One way to address these issues is to provide a patient side cart with asystem that provides a force to assist with moving the patient sidecart. Such a system may be a drive system that includes one or moredevices that drive or move a patient side cart so that a user need notprovide all of the force necessary to move the cart. For instance, adrive system may provide all of the force necessary to move a patientside cart or a drive system may provide a large majority of the forcenecessary to move a patient side cart so that a user may sense theweight and/or handling of the cart when the user applies a force to movethe cart.

A drive system for a patient side cart may interact with controls that auser operates to move the cart. To control the speed at which a patientside cart moves, the controls may include a throttle to provide an inputto a drive system of the cart. In such a case, the controls may alsoinclude a brake to control stopping of the patient side cart. Thecontrols would also require a steering device so that a user couldindicate to the drive system what direction a patient side cart shouldbe driven in. However, such an array of controls may be somewhatdifficult for a user to operate, particularly if the user is notfamiliar with the controls. Therefore, it may be desirable to provide apatient side cart with a drive system and controls that are relativelyeasy to operate in a simple manner.

Various exemplary embodiments of the present disclosure contemplate apatient side cart of a teleoperated surgical system in which the patientside cart includes a steering interface for a user that operates inconcert with a drive control system. One consideration in moving apatient side cart of a teleoperated surgical system is the ease withwhich the patient side cart may be moved by a user.

The steering interface may permit a user to move the patient side cartin a relatively easy and familiar manner without the use of multiplesteering and drive interface devices. A steering interface in accordancewith various exemplary embodiments may include “intelligence” in thatthey can enable the storage of various calibration data that can beprovided to a control processor that uses drive control algorithms formotor-assisted driving of the cart. Such data may be used for variouspurposes, such as to calibrate devices of the steering interface whichmay vary to a degree from one to another. For instance, data couldinclude calibration data for one or more sensors that are included inthe steering interface. Calibration of a component of a steeringinterface, such as a force sensor, may include storing calibration datain a data storage device of the steering interface. The calibration mayinclude, for instance, data that associates a force detected by a forcesensor with a signal that a drive system of a cart may use to controlmovement of a cart. The calibration data may associate the detectedforce with a signal for a drive system through an algorithm, such asthrough one or more equations, look up tables, or other functions.

The intelligence functions of the steering interface may be configuredto function automatically, such as when a steering interface isinitially mounted to a cart and connections are made between the cartand steering interface to permit transmittal of data to the cart. Forinstance, the calibration function of a steering interface may functionautomatically when the steering interface is mounted to a cart, causingstored data from a calibration device of the steering interface tocalibrate signals transmitted from one or more force sensors to a drivesystem of the cart.

In various exemplary embodiments, the steering interface may bereplaceable, e.g., in the field, such as when the steering interface orcomponent thereof is damaged or otherwise non-functional. In addition,if one or more components of a steering interface is damaged orotherwise requires repair, the steering interface could be removed sothe component may be repaired or replaced. Recalibration could also beconducted on components of a steering interface once the steeringinterface has been removed so that the steering interface is ready tofunction when the steering interface is attached to a cart. According toan exemplary embodiment, a steering interfaces described herein may beused with various carts, including carts of different sizes and/orconfigurations. Further, various exemplary embodiments contemplate asteering interface for a patient side cart of a teleoperated surgicalsystem.

Steering interfaces of the exemplary embodiments described herein may beprovided in various forms. According to one exemplary embodiment, asteering interface for a patient side cart of a teleoperated surgicalsystem may be provided in the form of a handlebar. However, the form orshape of the steering interface for a user of a patient side cart of ateleoperated surgical system is not limited to this exemplaryembodiment. For example, a steering interface for a patient side cartmay be in the form of a plurality of handlebars, one or more handles, asteering wheel, combinations of these interfaces, and other shapes andforms used for steering interfaces.

Teleoperated Surgical System

With reference to FIG. 1, a teleoperated surgical system 100 is providedwhich, in an exemplary embodiment, performs minimally invasive surgicalprocedures by interfacing with and controlling a variety of remotelyoperated surgical instruments, such as one or more surgical instruments102, as those of ordinary skill in the art are generally familiar. Thesurgical instruments 102 may be selected from a variety of instrumentsthat are configured to perform various surgical procedures, and inaccordance with various exemplary embodiments can have a variety ofconfigurations to implement surgical procedures of conventional surgicalinstruments. Non-limiting examples of the surgical instruments 102include, are but not limited to, instruments configured for suturing,stapling, cutting, grasping, applying electrosurgical energy (e.g.,cautery energy), and a variety of other instruments with which thosehaving ordinary skill in the art are generally familiar.

As illustrated in the schematic view of FIG. 1, the teleoperatedsurgical system 100 includes a patient side cart 110, a surgeon console120, and a control cart 130. In non-limiting exemplary embodiments ofthe teleoperated surgical system, the control cart 130 includes “core”processing equipment, such as core processor 170, and/or other auxiliaryprocessing equipment, which may be incorporated into or physicallysupported at the control cart 130. The control cart 130 may also includeother controls for operating the teleoperated surgical system. As willbe discussed in more detail below, in an exemplary embodiment, signal(s)or input(s) transmitted from surgeon console 120 may be transmitted toone or more processors at control cart 130, which may interpret theinput(s) and generate command(s) or output(s) to be transmitted to thepatient side cart 110 to cause manipulation of one or more of surgicalinstruments 102 and/or patient side manipulators 140 a-140 d to whichthe surgical instruments 102 are coupled at the patient side cart 110.It is noted that the system components in FIG. 1 are not shown in anyparticular positioning and can be arranged as desired, with the patientside cart 110 being disposed relative to the patient so as to affectsurgery on the patient. A non-limiting, exemplary embodiment of ateleoperated surgical system with which the principles of the presentdisclosure may be utilized is a da Vinci® Si (model no. IS3000)commercialized by Intuitive Surgical, Inc. of Sunnyvale, Calif.

In general, the surgeon console 120 receives inputs from a user, e.g., asurgeon, by various input devices, including but not limited to,gripping mechanisms 122 and foot pedals 124, and serves as a mastercontroller by which the instruments 102 mounted at the patient side cart110 act as slaves to implement the desired motions of the surgicalinstrument(s) 102, and accordingly perform the desired surgicalprocedure. For example, while not being limited thereto, the grippingmechanisms 122 may act as “master” devices that may control the surgicalinstruments 102, which may act as the corresponding “slave” devices atthe manipulator arms 140, and in particular control an end effectorand/or wrist of the instrument as those having ordinary skill in the artare familiar with. Further, while not being limited thereto, the footpedals 124 may be depressed to provide, for example, monopolar orbipolar electrosurgical energy, or to activate a variety of otherfunctions (e.g., suction, irrigation, etc.) at the instruments 102.

In various exemplary embodiments, suitable output units may include, butare not limited to, a viewer or display 126 that allows the surgeon toview a three-dimensional image of the surgical site, for example, duringthe surgical procedure, e.g., via an optical endoscope 103 at thepatient side cart 110. Other output units may include a speaker (orother component capable of transmitting sound), and/or a component withwhich a surgeon is in contact that can vibrate or the like to providehaptic feedback. In various exemplary embodiments, the one or moreoutput units may be part of the surgeon console 120 and signals can betransmitted from the control cart 130 thereto. Although in variousexemplary embodiments, one or more input mechanisms 122, 124 may beintegrated into the surgeon console 120, various other input mechanismsmay be added separately and provided so as to be accessible to thesurgeon during use of the system, but not necessarily integrated intothe surgeon console 120. In the context of the present disclosure, suchadditional input mechanisms are considered part of the surgeon console.

Thus, a “surgeon console” as used herein includes a console thatcomprises one or more input devices 122, 124 that a surgeon canmanipulate to transmit signals, generally through a control cart such as130 to actuate a remotely-controllable kinematic structure (e.g.,surgical instruments 102 mounted at arms 140) at the patient side cart110. The surgeon console 120 may also include one or more output devicesthat can provide feedback to the surgeon. As used herein, it should beunderstood, however, that a surgeon console can include a unit (e.g.,substantially as shown by element 120 in FIG. 1) that integrates thevarious input and output devices, with, for example, a display, but alsocan include separate input and/or output devices that are in signalcommunication with the controllers, such as controllers provided at thecontrol cart and accessible by a surgeon, although not necessarilyintegrated within a unit with various other input devices. As anexample, input units may be provided directly at the control cart 130and may provide input signals to a processor at the control cart. Assuch, a “surgeon console” does not necessarily require all of the inputand output devices to be integrated into a single unit and can includeone or more separate input and/or output devices.

The exemplary embodiment of FIG. 1 illustrates a patient side cart 110with multiple, independently moveable manipulator arms 140 that eachsupport an actuation interface assembly 146 and are configured to holdand manipulate various tools, including, but not limited to, forexample, a surgical instrument 102, and an endoscope imaging device 103.However, those having ordinary skill in the art will appreciate thatother patient side cart configurations may be used without departingfrom the scope of the present disclosure and claims.

Based on the commands input to input devices at, for example, thesurgeon console 120, the patient side cart 110 can position and actuatethe instrument(s) 102 to perform a desired medical procedure via theactuation interface assemblies 146 at the manipulator arms 140. Theactuation interface assemblies 146 are configured to engage withtransmission mechanisms 147 provided at a proximal end of the surgicalinstruments 102 (the general “proximal” and “distal” directions beingshown in FIG. 1 relative to the surgical instrument). The surgicalinstrument 102 and the actuation interface assembly 146 may bemechanically and/or electrically connected to be able to operate theinstrument 102. A patient side cart 110 may include a plurality ofwheels 149 mounted or otherwise attached to the cart 110, such as to abase 148 of the cart 110.

The teleoperated surgical system 100 can include a control system thatreceives and transmits various control signals to and from the patientside cart 110 and the surgeon console 120. The control system cantransmit light and process images (e.g., from an endoscope at thepatient side cart 110) for display, such as, e.g., display 126 at thesurgeon console 120 and/or on a display 132 associated with the controlcart 130.

In exemplary embodiments, the control system may have all controlfunctions integrated in one or more processors, such as a core processor170 at the control cart 130, or additional controllers (not shown) maybe provided as separate units and/or supported (e.g., in shelves) on thecontrol cart 130 for convenience. The latter may be useful, for example,when retrofitting existing control carts to control surgical instrumentsrequiring additional functionality, for example, by providing electricalenergy for use in monopolar and bipolar applications.

One of ordinary skill in the art would recognize that the controllers,e.g., core processor 170, provided at control cart 130 may beimplemented as part of a control system, which, as will be discussed inmore detail below, controls various functions of the present disclosure.One of ordinary skill in the art would recognize that functions andfeatures of the controllers, e.g., core processor 170, may bedistributed over several devices or software components, including, butnot limited to, processors at any of the surgeon console 120, patientside cart 110 and/or other devices incorporating processors therein.Functions and features of the control system, which may include coreprocessor 170, may be distributed across several processing devices.

Due to the size and overall configuration of a patient side cart,including the jointed arms, possibly mounted with one or more surgicalinstruments, moving a patient side cart may require a significantexertion of effort and can be cumbersome for a user. Further, it may bechallenging to move a patient side cart in a way in which it isrelatively easy to control the movements and steering of the patientside cart, due to the weight and size of the patient side cart.

Turning to FIG. 2, an exemplary embodiment of a patient side cart 310 isshown schematically. A patient side cart 310 may be arranged accordingto any of the exemplary embodiments described herein, such as withreference to FIG. 1 described above. For example, a patient side cart310 may include one or more patient side manipulator(s) 340, which canalso have one or more surgical instruments 302 installed thereat. Apatient side cart 310 may include wheels (not shown) on its base topermit movement of the cart. For example, a patient side cart 310 mayinclude three wheels or four wheels. One or more of the wheels may bedriven by a drive system included in the patient side cart 310 thatprovides motive force to the driven wheel(s), as will be discussedbelow.

According to an exemplary embodiment, a patient side cart may include asteering interface that receives input from a user indicating whatdirection the user would like the patient side cart to move in. Inaddition, the steering interface may receive input from a userindicating at what speed the user would like the patient side cart, suchas by detecting the amount of force a user applies to the device.

According to an exemplary embodiment, a patient side cart 310 of ateleoperated surgical system may include a steering interface 300, asshown in FIG. 2. In one exemplary embodiment, a steering interface 300may be configured as described in U.S. application Ser. No. 14/208,663,filed on Mar. 13, 2014 and claiming priority to U.S. ProvisionalApplication No. 61/791,924 entitled “Surgical Patient Side Cart withSteering Interface” and filed on Mar. 15, 2013, each of which is herebyincorporated by reference in its entirety. However, steering interfaceshaving other configurations also can be employed in conjunction with thedrive and control systems according to exemplary embodiments of thepresent disclosure. A steering interface 300 may be used to detectforces applied by a user to the steering interface 300, which in turnmay issue a signal to a controller of a drive system of a patient sidecart 310, which causes the patient side cart 310 to be driven andsteered in a desired manner. As shown in the example of FIG. 2, asteering interface 300 may be attached to a rear of a patient side cart310, with one or more manipulator arms 302 being located at a front ofthe patient side cart 310. However, the exemplary embodiments describedherein are not limited to a patient side cart 310 with a steeringinterface 300 attached to a rear, and the steering interface 300 mayinstead be mounted on other portions of a patient side cart 310, such asa front or side of the patient side cart 310.

Drive System

Information received at a steering interface may be used by a drivesystem of a patient side cart to provide motive force to one or moretransportation mechanisms of the cart. According to an exemplaryembodiment, a patient side cart may include one or more wheels astransportation mechanisms to move the cart in a desired direction. Oneor more of the wheels may be driven according to commands issued fromthe drive system of the patient side cart.

Turning to FIG. 3, a top schematic view of an exemplary embodiment of awheel arrangement for a patient side cart 400 is shown. A patient sidecart 400 may include one or more front wheels 410, 412 and one or morerear wheels 420, as shown in FIG. 3. The front of a patient side cart400 may be, for example, where manipulator arms are positioned. Thus,wheel 410 may be a front left wheel 410 while wheel 412 may be a frontright wheel 412.

According to an exemplary embodiment, one or more wheels of a patientside cart 400 may be driven. In one exemplary embodiment, the frontwheels 410, 412 of a patient side cart 400 of FIG. 3 may be driven whilerear wheels 420 are not driven. According to an exemplary embodiment,driven wheels may be individually driven by separate motors. Forinstance, motors 411, 413 may be provided to respectively drive wheels410, 412. Further, motors 411, 413 may drive wheels 410, 412independently. In other examples, wheels in the rear of a patient sidecart may be driven or all wheels of a patient side cart may be driven.Wheels that are driven may be fixed so that the wheels are preventedfrom turning. According to another embodiment, driven wheels may bepermitted to turn, either freely or in a controlled manner.

Wheels of a cart may be driven to produce a speed of, for example,approximately 1 meter per second when the manipulator arms of the cartare in a stowed, retracted position. Turning to FIG. 4, an exemplaryembodiment of a patient side cart 400 is shown in a stowedconfiguration. A patient side cart 400 may include a steering interface430 and a plurality of manipulator arms 402 holding surgical instruments(not shown), such as according to the embodiments of FIG. 1. In thestowed configuration shown in the example of FIG. 4, the manipulatorarms 402, and any respective instruments and other components installedthereon, may be folded into a relatively compact arrangement toward acenter of the patient side cart 400. Further, a post 404 upon which themanipulator arms 402 may be mounted may be in a non-extended, compactconfiguration as well. Those having ordinary skill in the art would befamiliar with various exemplary embodiments of patient side carts havingin which, for example, a central support post from which one or more ofthe passively jointed manipulator arms extend is provided in atelescoping arrangement so as to be raised and lowered relative to thebase of the cart. In a stowed configuration, therefore, the post can bein the lowered, non-extended position and the manipulator arms can bepositioned toward each other and proximate to a center portion of thecart.

According to an exemplary embodiment, a wheel that is not driven may bepermitted to spin freely as the patient side cart is driven and thewheel contacts a ground surface. For instance, rear wheels 420 of apatient side cart 400 may be permitted to turn in direction A indicatedin FIG. 3. According to an exemplary embodiment, one or more wheels mayhave a configuration similar to a caster wheel and may be permitted toturn freely about a vertical axis so that a wheel may turn in a left andright direction as a patient side cart changes direction. For instance,rear wheels 420 in FIG. 3 may have a configuration similar to a casterwheel and be permitted to turn freely about a vertical axis. Such wheelsmay also spin freely so that when a patient side cart is driven, freelyspinning wheels in contact with a ground surface also move. Wheels mayalso be turned by steering mechanisms, such as linkages and/or motors,according to steering input provided by a user.

Thus, according to one exemplary embodiment, a patient side cart 400 mayinclude front wheels 410, 412 that are driven and rear wheels 420 thatare not driven but are permitted to freely turn, as shown in FIG. 3. Inother words, the wheels of a patient side cart 400 may have aconfiguration and arrangement opposite to those of a shopping cartcommonly used in grocery stores and other retailers wherein the rearwheels (e.g., disposed proximate to the handle of the shopping cart) aredriven and the front wheels are castered. A patient side cart 400 with aconfiguration such as in the exemplary embodiment of FIG. 3 can minimizeor avoid relatively large sweeping motions, in particular at the frontof the cart opposite to where the steering interface is positioned.Minimizing such large sweeping motions at the front of the cart providesthe user with greater control in maneuvering the cart and minimizes therisk of collisions with the cart at the front of the cart wherevisibility by a user may be limited as a user maneuvers the cart fromthe rear end of the cart proximate the rear wheels 420.

As discussed above, when desiring to move the patient side cart 400, auser may engage a steering interface 430 of a patient side cart 400 andimpart a force to the steering interface 430 to indicate whichdirections the user desires the patient side cart 400 to move in. Forexample, a user may push the steering interface 430 in the foredirection (relative to the front wheels 410, 412 and the rear wheels420) along direction X in FIG. 3 or may pull the steering interface 430backwards in the aft direction along direction X in FIG. 3 to indicate adesire to move a patient side cart 400 either forward or backward.

In addition, a user may apply a force having at least a component in theY direction of FIG. 3 to indicate a desire to a turn the patient sidecart either to the left or right (relative to the front wheels 410, 412and the rear wheels 420 of the patient side cart 400). Forces applied inthe Y direction indicating a desire to turn a patient side cart 400 maybe used to provide a yaw control of the patient side cart 400 andcontrol turning of the cart 400. For instance, a user may apply alateral force to a steering interface 430 along directions substantiallyperpendicular to the forward and rearward directions of FIG. 3, whichmay substantially correspond to a direction along a Y direction or axis.The sensor configuration discussed above for detection of a forceapplied by a user to indicate a desired movement for a patient side cartis one exemplary way of sensing turning (e.g., yaw) and fore/aftsteering control, but other techniques also could be employed and sensorconfigurations modified accordingly. For instance, according to anotherexemplary embodiment, a user may indicate that the patient side cartshould turn by applying more force to one of a left portion and rightportion of the steering interface 430, in relation to a left-rightdirection extending along the Y axis in FIG. 3, than the other of theleft portion and the right portion. The steering interface 430 may beconfigured to detect the applied forces and issue a signal to thecontrol system of the drive system, which commands the drive system toturn in the direction desired by the user.

A patient side cart may include a drive system configured to receivesignal(s) from a steering interface (e.g., from one or more sensors atthe steering interface). A patient side cart may include a controlsystem or controller, which may be part of the drive system or aseparate device or system in communication with the drive system.Referring again to FIG. 3, for example, the control system may beconfigured to receive signal(s) or input(s) from a steering interface430 of a patient side cart 400 and, based upon the received input(s),issue one or more command outputs or outputs to control the drivenwheel(s) of the patient side cart 400, such as the driven front wheels410, 412 shown in FIG. 3. For example, a command output issued by thecontrol system for the drive system of a patient side cart may be acommand output to drive a wheel to move the cart in a forward orbackward direction, and/or a command output to drive a wheel in a way toprovide a yaw rate and turn the cart in a direction desired by a user.

Turning to FIG. 5, a schematic block diagram of one exemplary embodimentof a drive system 500 for a patient side cart is shown in communicationwith a steering interface 510. A steering interface 510 may beconfigured as a handlebar according to the embodiments described abovefor the steering interface 430 of FIG. 3, for example. For an exemplarysteering interface that can be used in conjunction with the Reference ismade to U.S. application Ser. No. 14/208,663, filed on Mar. 13, 2014 andclaiming priority to U.S. Provisional Application No. 61/791,924entitled “Surgical Patient Side Cart with Steering Interface” and filedon Mar. 15, 2013, each being incorporated by reference herein in itsentirety. The steering interface 510 may include one or more sensors todetect forces applied by a user to indicate a desired movement for apatient side cart. That is, as described above, the steering interfacecan include one or more sensors for sensing push/pull and turning forcesindicating a desire to move the cart in the fore/aft and left/rightdirections.

In the exemplary embodiment illustrated in FIG. 5, the steeringinterface 510 includes a first sensor 512 and a second sensor 514 thatdetect forces along the X and Y directions (as shown in FIGS. 3 and 5).In various exemplary embodiments, the sensors 512 and 514 can be loadcells. In an exemplary embodiment, the sensors 512 and 514 can beconfigured as those disclosed for use in the steering interfacedescribed in U.S. application Ser. No. 14/208,663, filed on Mar. 13,2014 and claiming priority to U.S. Provisional Application No.61/791,924 entitled “Surgical Patient Side Cart with Steering Interface”and filed on Mar. 15, 2013, each of which is incorporated by referenceherein in its entirety.

The steering interface 510 may issue or transmit a first input or signal516 from the first sensor 512 and a second input or signal 518 from thesecond sensor 514, which are received by the drive system 500 of apatient side cart that the steering interface 510 is attached to. Firstinput 516 and second input 518 may include information about forcesapplied by the user to the steering interface 510 to indicate a desiredmovement. For instance, first input 516 and second input 518 may eachinclude data corresponding to a force detected in the X direction ofFIG. 5 data, such as F_(x) data that will be discussed below, and datacorresponding to a force detected in the Y direction of FIG. 5, such asF_(y) data that will be discussed below.

Although first input 516 and second input 518 may be providedseparately, as shown in FIG. 5, first input 516 and second input 518 maybe combined or otherwise provided as a single input. Furthermore,although each of first input 516 and second input 518 may include bothdata for forces directed in the X direction and Y direction of FIG. 5,such as F_(x) data and F_(y) data, first input 516 and second input 518may instead be processed so that one input includes only F_(x) data andthe other input includes only F_(y) data when more than one input isprovided.

According to an exemplary embodiment, a steering interface 510 mayinclude a plurality of sensors, such as the first sensor 512 and thesecond sensor 514 shown in FIG. 5, so that information from the sensorsmay be combined or compared to determine a desired motion indicated by auser. For instance, F_(y) data from the first sensor 512 and from thesecond sensor 514 may be analyzed by the drive system 500 to determineif a user is applying a force to the steering interface 510 along the Ydirection to indicate a desire to turn a patient side cart. When theF_(y) data indicates a user's desire to turn a patient side cart, acommand output may be issued to cause the patient side cart to turn.F_(x) data from the first sensor 512 and from the second sensor 514 maybe similarly analyzed by the drive system 500 to determine a user'sdesire to move a patient side cart in a fore/aft direction, such asalong the X direction.

According to an exemplary embodiment, a patient side cart may includeone or more devices to condition signals received from a steeringinterface so that the signals may be further processed. As shown in FIG.5, a drive system 500 may include a signal conditioner 520, which mayinclude one or more devices with which those of ordinary skill in theart have familiarity. For instance, signal conditioner 520 may includean amplifier to increase the power of signals 516, 518. Signalconditioner 520 also may include an analog-to-digital converter toconvert analog signals 516, 518 to a digital form for furtherprocessing. Signal conditioner 520 may include these devices incombination with one another. Once signals 516, 518 have beenconditioned by signal conditioner 520, the signals may be sent via ahigh speed communication connection 522 to other components of the drivesystem 500. In a non-limiting example, the high speed communicationconnection 522 may be an RS422 type of connection.

Drive system 500 may further include a control system or controller 540,according to an exemplary embodiment. Control system 540 may beconfigured to receive signal(s) (which may be first conditioned andprocessed by signal conditioner 520) from a steering interface 510indicating a desired movement for a patient side cart, to analyze thereceived signals, and to issue one or more command outputs to cause thepatient side cart to move in the desired manner.

According to an exemplary embodiment, control system 540 may issue aseparate command output for each driven wheel to effect a desiredmovement for a patient side cart. For instance, if a patient side carthas a first driven wheel 560 and a second driven wheel 562, controlsystem 540 may issue or transmit a command output 542 for first drivenwheel 560 and a command output 544 for second driven wheel 562. Firstdriven wheel 560 may be, for example, a front left wheel, such as thefront left wheel 410 of the patient side cart 400 of FIG. 3, whilesecond driven wheel 562 may be, for example, a front right wheel, suchas the front right wheel 412 of the patient side cart 400 of FIG. 3.

According to an exemplary embodiment, drive system 500 may include oneor more devices to cause a desired movement of driven wheels 560, 562.For example, drive system 500 may include one or more devices 550, 552that cause wheels 560, 562 to move according to command outputs 542, 544issued from the control system 540. According to various exemplaryembodiments, drive devices 550, 552 can be motors, although other typesof devices familiar with those of ordinary skill in the art to causewheel motion according to a command output also can be utilized.According to an exemplary embodiment, each driven wheel may be providedwith its own drive device so that each driven wheel is independentlydriven. As shown in FIG. 5, first driven wheel 560 may be driven by afirst drive device 550 and second driven wheel 562 may be driven by asecond drive device 562.

A drive system for a patient side cart may include sensors and controlsto sense a movement of the cart, compare that movement with a movementdesired by a user, and adjust the movement of the cart accordingly.According to an exemplary embodiment, a drive system 500 can beconfigured to detect movement of a patient side cart and provide thedetected movement to the drive system 500 for possible correction. Thedetected movement may be used, for instance, in a feedback type ofcontrol. Movement of the cart may be detected indirectly, such as bydetecting information from various components that affect movement ofthe cart. For example, as shown in FIG. 5, a first sensor 570 may beused to detect the movement of the drive device 550 that drives drivenwheel 560 and a second sensor 572 may be used to detect the movement ofthe drive device 552 that drives driven wheel 562.

Signals from sensors 570, 572 may be sent to control system 540 andanalyzed to determine the speeds of driven wheels 560, 562. The controlsystem 540 can calculate a turning rate of a patient side cart, whichcan be determined on the basis of a difference in speed between thefirst driven wheel 560 and the second driven wheel 562. According to anexemplary embodiment, the information detected by sensors 570, 572 maybe used by control system 540 in a feedback arrangement. However, theembodiments described herein are not limited to a feedback controlscheme but instead may use other control schemes such as, for example, afeed forward control scheme may be used in one or more control blocks ofthe overall scheme. According to another exemplary embodiment, a drivesystem 500 may include other types of sensors to determine the movementof a patient side cart, such as an accelerometer and/or sensors thatdetect other components of the cart, such as a wheel or axle rotationalspeed. Further, the drive system 500 may be configured to minimize oreliminate deadbands so the drive system 500 is responsive, with littleto no delay between the force applied by a user to a steering interfaceand a desired movement of a patient side cart. For instance, thecomponents of a drive system 500 and/or steering interface 510 may beinclude high quality, responsive components or may be otherwiseconfigured to minimize any delay in their responsiveness.

According to an exemplary embodiment, control system 540 may limit thespeed of a patient side cart on a basis of the configuration of thecart. Control system 540 may analyze one or more signals indicating adesired movement of a patient side cart and issue one or more commandoutputs 542, 455 to driven wheels 560, 562 on a basis of theconfiguration of the cart. For instance, if a patient side cart is instowed configuration, such as in the exemplary embodiment of FIG. 4,control system 540 may permit a patient side cart to travel at a speedand/or acceleration desired by a user or limit the desired speed and/oracceleration by a small degree. Conversely, if the patient side cart isnot in a stowed configuration, such as when manipulator arms areextended, control system 540 may limit a desired speed and/oracceleration by a greater amount than when the cart is in the stowedconfiguration. The limitation on speed and/or acceleration may beimposed to minimize instability during travel of a cart. According to anexemplary embodiment, a first maximum speed and/or acceleration may beimposed by control system 540 when a patient side cart is in a stowedconfiguration and a second maximum speed and/or acceleration may beimposed when the cart is in a non-stowed configuration, with firstmaximum speed and/or acceleration being greater than the second maximumspeed and/or acceleration. However, the exemplary embodiments are notlimited to two maximum speeds and/or accelerations but instead mayprovide various maximums, such as varying the maximum speed and/oracceleration on a basis of the configuration of a cart, such as anextent to which the components of the cart, such as manipulator arms,are extended. Thus, control system 540 may control and limit a desiredspeed and/or acceleration for a patient side cart so that the carttravels at lower speeds and/or accelerations when the cart is innon-stowed configurations with extended manipulator arms than when thecart is in a stowed configuration with retracted manipulator arms.

According to an exemplary embodiment, a patient side cart may includeone or more sensors to determine the configuration of a patient sidecart. For instance, one or more sensors may detect the position ofmanipulator arms and provide signal(s) to control system 540 about themanipulator arm positions. Position sensor(s) may be, for example,proximity sensors, encoders connected to components of a patient sidecart, such as manipulator arm motors, and other position sensors used byone of ordinary skill in the art. Control system 540 may use thesignal(s) to determine what degree, if any, to limit a speed and/oracceleration of a patient side cart. Other methods may be used todetermine the position of components of a patient side cart. Forinstance, commands sent to drive motors of cart components, such as thedrives for manipulator arms, may be used to predict the location of thecomponents, input from a user providing information on the configurationof a cart may be used to determine a state of the cart, and otherlocation determining methods used in the art may be utilized. Further,the positions other components besides manipulator arms may be detectedwhen determining the configuration of a cart and to what degree adesired speed and/or acceleration should be limited.

Turning to FIG. 6, a schematic block diagram for an exemplary embodimentof a control system 600 for a drive system of a patient side cart isshown. Control system 600 may be used, for example, as the controlsystem 540 shown in FIG. 5. Control system 600 may receive one or moreinputs or signals from a steering interface, such as the steeringinterface 510 of FIG. 5. For instance, if a steering interface 510includes one or more sensors to measure forces applied by a user in theX and Y directions of FIG. 5, the sensors may detect the forces andissue signals corresponding to the forces. These signal(s) or input(s)may be received by a control system 600, which in turn may outputcommand outputs to drive wheels driven by the drive system.

For instance, a control system 600 may receive a signal or input F_(x),which may correspond to the force applied to the steering interface 510in the X direction of FIG. 5. Control system 600 may also receive asignal or input F_(y), which may correspond to the force applied to thesteering interface 510 in the Y direction of FIG. 5. For example, in theexemplary embodiment wherein steering interface 510 includes a pluralityof sensors 512, 514, as shown in FIG. 5, input F_(x) and input F_(y) mayrepresent inputs or signals from the plurality of sensors to indicatemovements along the X direction and the Y direction, respectively, thatare desired by a user of a patient side cart. As shown the exemplaryembodiment of FIG. 5, input F_(x) and input F_(y) may be providedseparately. In another embodiment, input F_(x) and input F_(y) may beprovided as a single input or signal. Further, each of input F_(x) andinput F_(y) may be provided as combined inputs from a plurality ofsensors of a steering interface (such that input F_(x) includes datafrom multiple sensors and input F_(y) includes data from multiplesensors), or separate F_(x) and F_(y) inputs may be provided from eachsensor of a steering interface.

A control system may include one or more control modules configured toreceive an input signal, such as a signal from a steering interface, andoutput a desired behavior. The desired behavior may be, for example, adesired overall movement for the patient side cart and/or may be desiredindividual movements for the driven wheels of a patient side cart. Forinstance, a signal corresponding to a force applied to a steeringinterface by a user can be analyzed and an output of a desired movementmay be provided. The desired movement of the cart may correspond to theforce applied to the steering interface. An output of a desired movementmay represent, for instance, a desired velocity and/or acceleration fora patient side cart. The input signal may be first conditioned and/orprocessed, such as by signal conditioner 520 of FIG. 5, before beingconverted to a desired behavior by a control module. The desiredbehavior may be, for example, one or more of a desired velocity,acceleration, and yaw (turning) rate.

According to an exemplary embodiment, a control system 600 may include afirst control module 610 and a second control module 612, as shown inFIG. 6. First control module 610 may be configured to receive signalF_(x), which may correspond to the force applied to the steeringinterface 510 in the X direction of FIG. 5, analyze signal F_(x), andoutput a desired fore/aft movement signal 602 along the X direction.Second control module 612 may be configured to receive signal F_(y),which may correspond to the force applied to the steering interface 510in the Y direction of FIG. 5, analyze signal F_(y), and output a desiredyaw rate signal 622 for a patient side cart to effect turning of thecart. The desired fore/aft movement signal 620 and the desired yaw ratesignal 622 may correspond to a desired velocity and/or accelerationalong the X and Y directions, respectively.

To perform the actions of analyzing input signals F_(x), F_(y) andgenerating desired movement signals, control modules 610, 612 mayinclude information that correlates forces applied to a steeringinterface along the X and Y directions to desired movements of thepatient side cart in the X and Y directions. For example, controlmodules 610, 612 may include maps, algorithms, look-up tables, or otherfunctions used in the art to correspond a force input to a steeringinterface to a desired movement of a patient side cart, such as adesired velocity and/or desired acceleration. According to an exemplaryembodiment, control modules 610, 612 may include one or more dampingparameters to affect the output of control modules 610, 612 in a desiredmanner, such as to control the variation of the output of controlmodules 610, 612 over time.

Once a signal corresponding to a desired movement, such as a desiredvelocity and/or desired acceleration, has been provided, a commandoutput that corresponds to the desired movement can be output. Forexample, components of a drive system, such as a motor driving a drivenwheel, may not be configured to receive a desired movement signal thatis in form of a desired velocity and/or desired acceleration and causethe desired movement of the cart without the desired movement signalbeing in the form of a force or a torque. In other words, a motordriving a driven wheel might be configured to receive a command signalthat is in the form of a force (or a torque, which could be interpretedby static scaling, for example) instead of in the form of a velocityand/or an acceleration, which the motor might not be capable ofinterpreting. Thus, desired movement signals represent an action oroutput that a component, such as a motor for a driven wheel, shouldperform as opposed to instructions or command outputs input to the motorto cause the desired movement. To achieve the desired movement, acontrol system may include one or more model sections configured toproduce command outputs, such as, for example, command outputscorresponding to a force or torque, that are based on signalscorresponding to a desired movement. The command outputs (e.g., in theform of a force or a torque) may be issued to components of a drivesystem that cause movement, such as a motor for a driven wheel.

Turning to FIG. 6, control system 600 may include a fore/aft modelsection or module 630 configured to receive a desired raw fore/aftmovement signal or input 620, analyze the signal, and issue or transmita fore/aft command output 640 corresponding to the desired movement.Fore/aft command output 640 may be, for example, a command output to amotor to drive a driven wheel in a way that will produce the desiredfore/aft movement. For instance, fore/aft command output 640 may be inthe form of a force or a torque command for a motor that drives a drivenwheel. Control system 600 may also include a yaw model section or module632 configured to receive a desired raw yaw signal or input 622, analyzethe signal, and issue or transmit a yaw rate command output 642corresponding to the desired yaw rate for turning a patient side cart.Yaw rate command output 642 may be in the form of a differentialvelocity between driven wheels or a torque command for motors that drivedriven wheels. Thus, yaw rate command output 642 may be, for example, acommand output to motors of a drive system to produce a torque that willcause a patient side cart to turn in a desired manner. For example, if adrive system 500 includes a first driven wheel 560 and a second drivenwheel 562, yaw rate command output 642 may cause the driven wheels 560,562 to rotate at different speeds to produce an overall torque for apatient side cart that will cause the cart to turn.

According to an exemplary embodiment, model sections 630, 632 can beseparate sections or modules of a control system 600, as shown in FIG.6, or may be a single section or module (not shown).

First command output 640 and second command output 642 may be furtherprocessed to provide particular command outputs for individual drivenwheels. For example, if a patient side cart has a first driven wheel 560and a second driven wheel 562, as shown in FIG. 5, first command output640 and second command output 642 may be further processed by controlsystem 600 to provide separate command outputs 542, 544 for first drivenwheel 560 and second drive wheel 562, as shown in FIG. 5. Commandoutputs 542, 544 may be the same or may differ, depending upon thedesired movement for a patient side cart and the command outputs fordriven wheels 560, 562 that effect the desired movement.

To convert a desired movement of a patient side cart, such as a desiredvelocity and/or acceleration, into command outputs for operation of thedrive system, such as a force or a torque command for a motor, modelsections 630, 632 of a control system 600 may include models configuredto receive an incoming signal, such as the desired fore/aft signal 620and the desired yaw rate signal 622, and issue a command output to causea patient side cart to move in a desired manner. According to anexemplary embodiment, a model may correlate a desired movement to acommand output for causing the desired movement, for example, byaccounting for the kinematics of a patient side cart, such as the massand configuration of cart. A map, algorithm, functional equation,look-up table, or other technique with which those of ordinary skill inthe art would understand can be used to convert a signal indicative of adesired motion, such as a desired velocity and/or acceleration, into acommand output, such as a force or torque, for producing the desiredmotion.

In various exemplary embodiments, an inverse model can be used for modelsections 630, 632. An inverse model may be implemented by receiving adesired behavior, such as, for example, a desired motion of the patientside cart, as an input and outputting a command to achieve the behavior.In other words, rather than modeling a cart's behavior by receiving acommand, such as a force or torque, as an input and outputting apredicted behavior for the cart, such as a velocity and/or acceleration,an inverse model does the reverse.

According to an exemplary embodiment, fore/aft model section 630 caninclude an inverse model configured to receive a desired fore/aftmovement signal 620, which may correspond to a desired velocity and/oracceleration, and output a fore/aft command output 640, which mayrepresent a force or a torque, based on the modeled fore/aft behaviorfor a patient side cart. The output fore/aft command output 640 may thenbe received by, for example, a motor, which interprets the output/foreaft command output 640 signal and drives a driven wheel on the basis ofthe command output 640. Similarly, yaw model section 632 can include aninverse model configured to receive a desired yaw rate signal 622, whichmay correspond to a desired velocity and/or acceleration, and output ayaw rate command output 642, which may represent a force or a torque,based on the modeled fore/aft behavior for a patient side cart. Theoutput yaw rate command output 642 may then be received by, for example,one or more motors, which interpret the yaw rate aft command output 642signal and drive one or more driven wheels on the basis of the commandoutput 640 to turn a patient side cart.

To provide a drive system that is relatively accurate and stable, invarious exemplary embodiments, a control system may include a feedbackcontrol that measures the motion of a patient side cart and feedsinformation about the motion of the cart back into the control system.Turning to FIG. 7, an exemplary embodiment of a control system includingfeedback control is shown. The control system of FIG. 7 may, forexample, be used as the control system 540 of FIG. 5. As shown in FIG.7, an input signal 652 may be provided to a control module 660 of thecontrol system that produces a desired movement signal 662. Input signal652 may correspond to signals F_(x), F_(y) of FIG. 6, control module 660may correspond to control modules 610, 612 of FIG. 6, and desiredmovement signal 662 may correspond to desired movement signals 620, 622of FIG. 6. According to an exemplary embodiment, control module 660 anda model section 670 may be arranged in a feed forward arrangement, withdesired movement signal 662 fed to model section 670. The desiredmovement signal 662 is received by model section 670, which produces acommand output 672 that is sent to a driven component 680 of a patientside cart to cause the desired movement. A driven component 680 may be adriven wheel of a patient side cart, such as one of front wheels 410,412 shown in FIG. 3. Model section 670 may correspond to model sections630, 632 of FIG. 6 and command output 672 may correspond to commandoutputs 640, 642 of FIG. 6.

The feedback portion of a control system can measure the output 682 ofthe driven component 680, such as a velocity, acceleration, and/or yawrate. For example, a sensor may be configured to detect the velocity,acceleration, and/or yaw rate of one or more driven wheels or of thecart as a whole. For instance, a sensor may be configured to detect adriven wheel rotational velocity (or the angle, which can be used toderive the rotational velocity). The output 682 may then be fed back andcompared to a desired movement signal 662 produced by the control module660, such as at an error detector 664.

If the error detector 664 determines that the output 682 and the desiredmovement signal 662 differ, an error signal or output 666 is providedthat is indicative that the patient side cart is not moving as desired.The error output 666 is input to a feedback control module 690. Theerror output 666 may represent a difference between the output 682 andthe desired movement signal 662. The feedback control module 690 maygenerate a feedback command output 692 that is combined with the commandoutput 672, such as at an adder 674. Feedback command output 692 andcommand output 672 may be combined to produce a corrected command output694 that is provided to the driven component 680 to provide a moreaccurate and stable control of the movement of a patient side cart.

According to an exemplary embodiment, a patient side cart may includefeedback control for each of fore/aft movement and yaw rate control. Asdiscussed above, providing feedback control may provide more accurateand stable controls for a patient side cart. These advantages may beprovided for each of the fore/aft and yaw components of a patient sidecart's movements.

Referring now to FIG. 8, a schematic block diagram is shown for anexemplary embodiment of a control system 700 for a patient side cartthat includes feedback control for fore/aft movement and yaw ratecontrol. As shown in FIG. 8, the control system 700 receives one or moreinput signals, such as F_(x), F_(y), as discussed above in reference toFIG. 6. A first control module 710, which may correspond to controlmodule 610 of FIG. 6, may receive input signal F_(x) and output adesired fore/aft movement signal 712. A fore/aft model section 730,which may correspond to fore/aft model section 630 of FIG. 6, mayreceive the desired fore/aft movement signal 712 and output a fore/aftcommand output 732. Similarly, a second control module 720, which maycorrespond to control module 612 of FIG. 6, may receive input signalF_(y) and output a desired yaw rate signal 722 to a yaw rate modelsection 740, which may correspond to yaw model 632 of FIG. 6, whichissues a yaw rate command output 742.

To provide specific command outputs to individual driven wheels of apatient side cart, control system 700 may include a cart dynamicssection 780 configured to receive fore/aft command output 732 and yawrate command output 742 and issue command outputs for individual wheelsthat will cause a patient side cart to move in the fore/aft directionand turn at the desired yaw rate. For instance, cart dynamics section780 may analyze the fore/aft command output 732 and the yaw rate commandoutput 742 and issue a left driven wheel torque command output 796 and aright driven wheel torque command output 798. According to an exemplaryembodiment, command outputs may be provided to motors that driven thedriven wheels of a patient side cart. According to an embodiment, leftdriven wheel torque command output 796 may be issued for a left frontwheel of a patient side cart, such as to the motor for the left frontwheel 410 of FIG. 4, and right driven wheel torque command output 798may be issued for a right front wheel of a cart, such as to the motorfor the right front wheel 412 of FIG. 3.

Left driven wheel torque command output 796 and a right driven wheeltorque command output 798 may be the same or may differ. For instance,if the force applied by a user to a steering interface indicates adesire to move a patient side cart forwards or backwards along astraight line, such as along the X direction of FIG. 3, the left drivenwheel torque command output 796 and a right driven wheel torque commandoutput 798 may be the same to cause a left front wheel and a right frontto have the same torque and rotate at the same rate.

However, if the force applied by a user to a steering interfaceindicates a desire to turn a patient side cart, such as in a directionhaving a Y direction component as shown in FIG. 3, the left driven wheeltorque command output 796 and a right driven wheel torque command output798 may differ so that the left front wheel and the right front wheelrotate at different rates, which may cause a torque that turns a patientside cart at the desired yaw rate. By configuring a drive system of apatient side cart to turn the cart by turning driven wheels at differentspeeds, the cart may be advantageously permitted to pivot about a pointlocated between the driven wheels. This may provide smoother, tighterturning in comparison to a cart that pivots about a point locatedoutside (not between) the driven wheels of the cart.

To provide feedback control, output signals may be provided from cartdynamics section 780 and fed back within the control system 700. Forinstance, cart dynamics section 780 may provide a fore/aft output signal792 and a yaw rate output signal 794. As shown in FIG. 8, fore/aftoutput signal 792 may be compared with the desired fore/aft movementsignal 712, such as at error detector 714, and yaw rate output signal794 may be compared with the desired yaw rate signal 722, such as aterror detector 724. Any differences resulting from the comparison aterror detectors 714, 724 are sent to feedback control modules 750, 760,respectively. Fore/aft feedback control module 750 may be configured toproduce a fore/aft feedback command output 752, which is combined withthe fore/aft command output 732, such as at adder 772, to provide acorrected fore/aft command output 776, which is in turn sent to cartdynamics section 780. Yaw feedback control module 760 may be configuredto produce a yaw rate feedback command output 762, which is combinedwith the yaw rate command output 742, such as at adder 774, to provide acorrected yaw rate command output 778, which is in turn sent to cartdynamics section 780.

A patient side cart may include features or embodiments in addition tothose discussed above. For example, although it is desired that a drivesystem of a patient side cart will provide motive force to move the cartso that minimal effort will be required from a user, it may be desirablefor the drive system to not provide all of the force necessary to movethe cart in a desired manner. According to an exemplary embodiment, thedrive system of a patient side cart may provide the majority of theforce necessary to move the cart but require a user to provide a smalldegree of the force. In this way, the user may feel the mass andhandling of the cart when pushing or pulling the cart. Thus, the usermay understand how massive the cart may be and how smoothly the cartmoves so the user may appreciate the care that should be used whenmoving the cart. According to an embodiment, a control system of apatient side cart may include one or more filters to affect the commandoutputs issued to the driven wheels of the cart, such as by reducing theamount of torque applied to the wheels or by reducing a desired velocityor acceleration for the driven wheels.

According to an exemplary embodiment, a patient side cart may includeone or more safety devices to cut power for the drive system when apatient side cart is not being moved. For example, a steering interfacemay include one or more “dead man” switches, as discussed in U.S.application Ser. No. 14/208,663, filed on Mar. 13, 2014 and claimingpriority to U.S. Provisional Application No. 61/791,924 entitled“Surgical Patient Side Cart with Steering Interface” and filed on Mar.15, 2013, each of which is incorporated by reference herein in itsentirety. Thus, when a user is not applying a sufficient force to asteering interface, the steering interface may stop providing a signalfrom the “dead man” switch. When such a signal is no longer received bythe drive system of a patient side cart, the drive system may beconfigured to cease power to driven wheels to stop movement of the cart.In addition, a patient side cart may include a manual brake control oran emergency kill switch for a user to cut power to the cart.

When the “dead man” switch is released, the drive system of a cart maybe configured to bring the cart to an immediate stop, according to anexemplary embodiment. For instance, the drive system may apply brakes tobring the cart to an immediate stop. According to an exemplaryembodiment, a brake mechanism may be configured to brake a driven wheelof a cart, such as, for example, one or both of front wheels 410, 412 ofthe exemplary embodiment of FIG. 3. However, the exemplary embodimentsdescribed herein are not limited to braking only driven wheels of acart. According to an exemplary embodiment, a brake mechanism may beconfigured to brake a non-driven wheel of a cart, such as, for example,one or both of non-driven rear wheels 420 of the exemplary embodiment ofFIG. 3. According to another exemplary embodiment, both driven wheelsand non-driven wheels may be braked.

In one exemplary embodiment, braking can be accomplished by a brakemechanism alone without any use of motors to decelerate a cart, such asthe motors 411, 413 of the exemplary embodiment of FIG. 3. According toanother exemplary embodiment, a cart may be gradually decelerated once a“dead man” switch has been released to bring the cart to a smootherstop, in comparison to when braking is immediately applied upon releaseof the “dead man” switch. For instance, one or more motors may be usedto gradually decelerate a cart over a period of time, such as byapplying a negative torque to wheels connected to the motors. In anotherexemplary embodiment, if the drive wheels are pivotable, directions ofthe drive wheels could be changed in a pair-wise manner so that thedrive wheels oppose each other, thus increasing friction to achievedeceleration. The period of deceleration may depend, for example, uponthe speed of the cart at the time the “dead man” switch is released. Invarious exemplary embodiments, the period of deceleration may increaseas the speed of the cart increases. The cart speed used to determine theperiod of deceleration may be, for example, an actual cart speed or atarget cart speed at the time the “dead man” is released. Once theperiod of deceleration has passed, brakes may be applied to bring thecart to a stop.

In another exemplary embodiment, the brakes of a cart may be configuredto apply a variable braking force. For example, the brakes can apply afirst, lower level of braking force during the period of decelerationand then apply a second, higher level of braking force to bring the cartto a stop once the period of deceleration has ended.

According to an exemplary embodiment, the “dead man” switch may be usedto overcome a fault status for a patient side cart to permit the cart tobe moved. A fault may occur, for example, when a problem occurs with adrive motor, which may cause the brakes of the cart to be automaticallyengaged to minimize or prevent further movement of the cart while thecart has a fault status. The “dead man” switch may be depressed by auser to disengage the brakes to place the cart in a neutral,“free-wheeling” state that permits a user to push the cart to adifferent location, even when the cart has a fault status. According toan exemplary embodiment, when the cart is in a neutral, free-wheelingstate, motor windings may be opened to prevent electromechanicalbraking, which may otherwise result if the windings were closed.According to an exemplary embodiment, if the “dead man” switch isreleased before the fault condition is cleared, the brakes of the cartare reengaged. If the “dead man” switch is depressed by a user at thesame time when a fault condition occurs, the controls may be configuredto sense release of the “dead man” switch followed by re-depression ofthe switch to cause disengagement of the brakes.

A “dead man” switch may have various levels of sensitivity correspondingto differing actions performed by a patient side cart, according to anexemplary embodiment. For instance, when the “dead man” switch is notdepressed, power is not supplied to the drive system of the cart. Whenthe “dead man” switch is depressed by application of a first amount offorce, the cart functions normally and the brakes of the cart are notengaged. When the “dead man” switch is depressed by application of asecond amount of force greater than the first amount of force, the cartmay be deactivated, such as by cutting power to the drive system of thecart. According to an exemplary embodiment, the second amount of forcemay correspond to a situation in which a user firmly grasps a handle ofthe cart when the user is alarmed, such as due to a flight or fightresponse. Because the user is alarmed and reacts by grasping the handleeven more firmly, rather than releasing the handle, the cart would nototherwise be deactivated (such as when the “dead man” switch isreleased). Thus, making the “dead man” switch sensitive to the second,higher amount of pressure permits the drive system of a cart to bedisengaged when a user presses the “dead man” switch with the second,higher amount of force, such as when the user is alarmed and grasps ahandle of the cart more firmly.

According to an exemplary embodiment, the drive system of a patient sidecart may include traction control. During movement of a patient sidecart, one or more wheels of the cart may lose traction with a groundsurface, such as when the ground surface is slippery or when inertialloads during movement of the cart or when traversing hills of variousslopes in various directions, resulting in a transfer of weight from onewheel to another. When the drive system of a cart includes tractioncontrol, the cart may respond to traction loss by changing commands todrive motors for wheels so that motion of cart corresponds to a motiondesired by a user to a greater degree, in comparison to when the cart isexperiencing a loss of traction. For instance, when a particular wheelloses traction, the speed of the contact surface for that particularwheel relative to the ground may become non-zero. According to anexemplary embodiment, a drive system of a cart may respond to a loss oftraction for a particular wheel by reducing the driving or brakingtorque applied to that particular wheel. Turning to FIG. 9, a topschematic view of an exemplary embodiment of a wheel arrangement for apatient side cart 800 is shown, includes driven front wheels 810, 812and rear wheels 820, 822. In the exemplary embodiment of FIG. 9, drivenfront wheel 810 has encountered a low friction region 830 of a groundsurface, resulting in a loss of traction for front wheel 810. Inresponse to the loss of traction for front wheel 810, a drive system ofa cart may reduce the magnitude of the torque for front wheel 810 toreduce slip between front wheel 810 and the ground surface. Thedirection of the torque for front wheel 810 may be either positive(e.g., for acceleration) or negative (e.g., for deceleration). Accordingto an exemplary embodiment, the torque for driven front wheel 812 mayalso be adjusted, which may result in a reduction in the control of cart800 in a fore/aft direction 840 but enhancement of the control of cart800 in a yaw direction 842. In other words, control of cart 800 infore/aft direction 840 may be sacrificed via traction control so thatcart 800 may be controlled in yaw direction 842. For instance, if onlywheels 810, 812 are driven and wheel 810 loses traction, virtually onlyone degree of freedom may remain for controlling the motion of cart 800via driven wheel 812. Thus, a drive system for cart 800 may beconfigured to control the motion of cart 800 in yaw direction 842, suchas by adjusting the torque for wheel 812, instead of controlling themotion of cart in fore/aft direction 840 while wheel 810 lacks traction.

According to an exemplary embodiment, a drive system of a patient sidecart (such as the drive system 500 of the exemplary embodiment of FIG. 5and a drive system including the control systems of the exemplaryembodiments of FIGS. 6-8) may include one or more devices to determinewhen a loss of traction occurs. For instance, traction loss may bedetected by a sensor, such as, for example, a yaw rate sensor. Accordingto another exemplary embodiment, traction loss may be determined by amodel of the dynamics of a patient side cart and a model of the dynamicsof the stand-alone wheel. For instance, one model may provide thebehavior of the cart when a loss of traction occurs between one or morewheels, such as one or more driven wheels, and a ground surface andanother model may provide the behavior of the cart when no slip occurs,which may also be used to correct the behavior of the cart when there isa loss of traction. According to an exemplary embodiment, when a drivesystem of a cart uses speed control (e.g., commands the cart to move ata certain speed), the drive system could analyze the input for aparticular wheel to determine if the drive command is below apredetermined threshold indicating a loss of traction. The input to beanalyzed may be, for example, the inertia, torque, and/or power of thewheel. When speed control is used for a cart and a wheel of the cartloses traction, the input for that wheel likely decreases as the drivesystem maintains a desired speed of the cart. Thus, the drive system mayanalyze inputs for the various wheels of a cart to determine whether theinput has diminished below a predetermined threshold. According toanother exemplary embodiment, a drive system may analyze an input todetermine if the input is below a predetermined threshold for apredetermined amount of time to determine when a loss of traction isoccurring.

According to an exemplary embodiment, a drive system may determine theinertia of a wheel to determine whether a loss of traction is occurring.For instance, by knowing a wheel torque and an acceleration of a wheel,one may determine the inertia of a wheel. When a wheel of a cart haslost traction with a ground surface, the inertia of the wheel isrelatively low because the inertia is substantially that of just thewheel. Conversely, the inertia is higher when the wheel has tractionwith the ground surface because the measured inertia is not only that ofthe wheel but also at a least a portion of the cart. A drive system of acart may determine whether the inertia is lower than a predeterminedinertia threshold. When the inertia is lower than the threshold, thedrive system determines that the wheel has lost traction and enacts yawcontrol. According to an exemplary embodiment, the drive system mayrepeat its determination of wheel inertia and compare the inertia to thethreshold, continuing to enact yaw control until the drive systemdetermines that the inertia is greater than the threshold, whichindicates that traction has been restored.

According to an exemplary embodiment, instead of using a predeterminedinertia threshold and enacting traction control if a wheel inertia fallsbelow the threshold, a drive system may implement a continuum for motioncontrol. For instance, once inertia has been determined for a wheel, adrive system may determine where the determined wheel inertia falls on acontinuum ranging from a small inertia, which may correspond to a wheelthat lacks traction, to a large inertia, which may correspond to a cartwheel having traction. The drive system may then use a control valuecorresponding to where the wheel inertia falls on the spectrum whenusing traction control. Thus, the traction control utilizing a continuummay be sensitive to the amount of slipping and control movementaccording to the amount of slipping.

According to another embodiment, a patient side cart may include a kickplate. As shown in the exemplary embodiment of FIG. 2, a kick plate 320having a sensor may be located at the rear of a patient side cart, e.g.,the side of the cart where the steering interface is located. A steeringinterface 300 may be designed according to a situation when a user ispushing off of a ground surface to apply a force to the steeringinterface 300. However, if a user puts a foot on the back of a patientside cart in an attempt to help move the cart forward, whilesimultaneously holding the steering interface 300, there may be atendency to pull back on the steering interface in the X (aft)direction. In this situation, since the force applied to the steeringinterface 300 is in the X (aft) direction, the cart would move backwardin the aft direction toward the user, even though the user is attemptingto move the cart forward by using the user's foot. To prevent thissituation, the kick plate 320 can be configured to send a signal to stoppower to drive the cart when a user engages or strikes the kick plate320. For a further explanation regarding an embodiment of a kick platethat can be used, reference is made to U.S. application Ser. No.14/208,663, filed on Mar. 13, 2014 and claiming priority to U.S.Provisional Application No. 61/791,924 entitled “Surgical Patient SideCart with Steering Interface” and filed on Mar. 15, 2013.

According to an exemplary embodiment, a patient side cart may include asystem to prevent or minimize collisions between the cart and otherobjects. For example, a patient side cart may include radar or a lightdetection and ranging (LIDAR) system that detects objects in the path ofthe cart and issues a signal to the control system of the cart warningof a possible collision, which may cause the cart to stop.

According to an exemplary embodiment, the drive system also may beconfigured to adjust the wheels of a patient side cart to permit thecart to move in sideways manner. For instance, driven wheels 410, 412 inFIG. 3 may be rotated left or right ninety degrees (e.g., from theirposition shown in FIG. 3) and locked into that orientation so that cart400 may be permitted to move only sideways along the Y direction.According to an exemplary embodiment, such a rotation of wheels may beactuated by a control located on the steering interface of a patientside cart. Because wheels 420, 422 may be free to rotate, wheels 420,422 will follow the movement of wheels 410, 412. Such a configurationmay permit a patient side cart to enter relatively tight spots and movein a manner that would be otherwise difficult by turning cart via drivenwheels 410, 412 as discussed above. In this mode of transportation,force on the steering interface 400 in the Y direction will causesideways movement either to the left or the right depending on thedirection the force is exerted on the steering interface 400 in the Ydirection.

By providing a patient side cart with a drive system, the relativelylarge weight of the cart may be moved without requiring the user toprovide the force necessary to move the patient side cart without thedrive system. Further, the drive system may include a relativelyaccurate and stable control system that uses modeled behavior of thecart and feedback control.

Exemplary embodiments, including the various operational methodsdescribed herein, can be implemented in computing hardware (computingapparatus) and/or software, such as (in a non-limiting example) anycomputer that can store, retrieve, process and/or output data and/orcommunicate with other computers. The results produced can be displayedon a display of the computing hardware. One or more programs/softwarecomprising algorithms to affect the various responses and signalprocessing in accordance with various exemplary embodiments of thepresent disclosure can be implemented by a processor, such as datainterface module, of or in conjunction with the control cart includingcore processor and may be recorded on computer-readable media includingcomputer-readable recording and/or storage media. Examples of thecomputer-readable recording media include a magnetic recordingapparatus, an optical disk, a magneto-optical disk, and/or asemiconductor memory (for example, RAM, ROM, etc.). Examples of themagnetic recording apparatus include a hard disk device (HDD), aflexible disk (FD), and a magnetic tape (MT). Examples of the opticaldisk include a DVD (Digital Versatile Disc), a DVD-RAM, a CD-ROM(Compact Disc-Read Only Memory), and a CD-R (Recordable)/RW.

Further modifications and alternative embodiments will be apparent tothose of ordinary skill in the art in view of the disclosure herein. Forexample, the systems and the methods may include additional componentsor steps that were omitted from the diagrams and description for clarityof operation. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the present teachings. It isto be understood that the various embodiments shown and described hereinare to be taken as exemplary. Elements and materials, and arrangementsof those elements and materials, may be substituted for thoseillustrated and described herein, parts and processes may be reversed,and certain features of the present teachings may be utilizedindependently, all as would be apparent to one skilled in the art afterhaving the benefit of the description herein. Changes may be made in theelements described herein without departing from the spirit and scope ofthe present teachings and following claims.

It is to be understood that the particular examples and embodiments setforth herein are non-limiting, and modifications to structure,dimensions, materials, and methodologies may be made without departingfrom the scope of the present teachings.

Other embodiments in accordance with the present disclosure will beapparent to those skilled in the art from consideration of thespecification and practice of the invention disclosed herein. It isintended that the specification and examples be considered as exemplaryonly, with a true scope and spirit being indicated by the followingclaims.

What is claimed is:
 1. A cart for supporting one or more instruments fora computer- assisted procedure, comprising: a base; a support structureextending from the base and adjustable to two or more differentconfigurations, the support structure comprising one or more interfacesconfigured to support one or more instruments to perform the procedure;a configuration sensor arranged to detect the configuration of thesupport structure; a steering interface configured to be grasped by auser to steer the base of the cart; a force sensor mechanism arranged todetect a force applied to the steering interface in response to thesteering interface being grasped to steer the base of the cart; and adrive system comprising a drive control module and a driven wheel, thedrive control module being operably coupled to receive: an input fromthe force sensor mechanism in response to detection of force by theforce sensor mechanism, and information about the two or more differentconfigurations of the support structure from the configuration sensor,the drive control module being operably coupled to output a movementcommand in response to the input received from the force sensormechanism and information received about the two or more differentconfigurations of the support structure, the driven wheel being mountedto the base of the cart and operably coupled to the drive controlmodule, and the driven wheel being operable to impart motion to the baseof the cart in response to the movement command output by the drivecontrol module.
 2. The cart of claim 1, wherein: a first configurationof the two or more different configurations comprises a stowedconfiguration; and a second configuration of the two or more differentconfigurations comprises an extended configuration.
 3. The cart of claim2, wherein: on the condition that the support structure is in theextended configuration, the movement command comprises a first commandto control at least one of velocity or acceleration of the base of thecart within a first range of values; and on the condition that thesupport structure is in the stowed configuration, the movement commandcomprises a second command to control the at least one of velocity oracceleration of the base of the cart within a second range of valuesdifferent from the first range of values.
 4. The cart of claim 1,wherein: the first range of values has a first maximum value; the secondrange of values has a second maximum value; and the second maximum valueis larger than the first maximum value.
 5. The cart of claim 3, wherein:the two or more different configurations comprise a range of partiallyextended configurations between the stowed configuration and theextended configuration, and on the condition that the support structureis in the range of partially extended configurations, the movementcommand comprises a third command to control the at least one ofvelocity or acceleration of the base of the cart within a third range ofvalues different from the first range of values or the second range ofvalues.
 6. The cart of claim 5, wherein: the first range of values has afirst maximum value; the second range of values has a second maximumvalue; the third range of values has a third maximum value within thethird range of values; and the third maximum value is between the firstmaximum value and the second maximum value.
 7. The cart of claim 6,wherein: the third maximum value varies over the range of partiallyextended configurations of the support structure.
 8. The cart of claim1, wherein the configuration sensor comprises at least one of aproximity sensor and a position encoder.
 9. The cart of claim 1, furthercomprising: a sensor arranged to detect a speed of the driven wheel; thedrive control module being operably coupled to receive a detected speedof the driven wheel from the sensor.
 10. The cart of claim 1, wherein:the drive system further comprises a feedback control module; the drivecontrol module is operably coupled to receive a feedback command fromthe feedback control module; the feedback command is based on adifference between a sensed movement of the cart and a desired movementof the base of the cart based on the movement command; and the drivecontrol module is operable to correct the movement command based on thefeedback command.
 11. An apparatus for controlling movement of a base ofa cart for a computer-assisted procedure, the apparatus comprising:means for supporting one or more instruments to perform acomputer-assisted procedure, the means for supporting adjustable to twoor more differing configurations; means for detecting a configuration ofthe means for supporting; means for steering the base of the cart; meansfor detecting a force applied to the means for steering; means foroutputting a movement command based on the configuration of the meansfor supporting and the force applied to the means for steering; andmeans for driving the base of the cart based on the movement command.12. The apparatus of claim 11, wherein the two or more differingconfigurations comprise a stowed configuration and an extendedconfiguration, wherein the movement command controls the means fordriving within a first range of values of at least one of velocity oracceleration on the condition that the means for supporting is in thestowed configuration and within a second range of values of at least oneof velocity or acceleration on the condition that the means forsupporting is the extended configuration.
 13. The apparatus of claim 11,wherein the two or more differing configurations comprise a stowedconfiguration and an extended configuration, wherein the movementcommand controls the means for driving within a first range of values ofat least one of velocity or acceleration on the condition that theconfiguration of the means for supporting is the stowed configuration,within a second range of values of at least one of velocity oracceleration on the condition that the configuration of the means forsupporting is the extended configuration, and within a third range ofvalues of at least one of velocity or acceleration on the condition thatthe means for supporting is within a range of partially extendedconfigurations between the stowed configuration and the extendedconfiguration.
 14. The apparatus of claim 13, wherein: a maximum valueof the first range of values is larger than a maximum value of thesecond range of values; and a maximum value of the third range of valuesis between the maximum value of the first range of values and themaximum value of the second range of values.
 15. The apparatus of claim14, wherein: the maximum value of the third range of values varies overthe range of partially extended configurations.
 16. A cart forsupporting one or more instruments for a computer-assisted procedure,comprising: a base; a support structure extending from the base andadjustable to two or more different configurations, wherein a firstconfiguration of the two or more different configurations comprises astowed configuration and wherein a second configuration of the two ormore different configurations comprises an extended configuration, thesupport structure comprising one or more interfaces configured tosupport one or more instruments to perform the procedure; a steeringinterface configured to be grasped by a user to steer the base of thecart; a force sensor mechanism arranged to detect a force applied to thesteering interface in response to the steering interface being graspedto steer the base of the cart; and a drive system comprising a drivecontrol module and a driven wheel, the drive control module beingoperably coupled to receive an input from the force sensor mechanism inresponse to detection of force by the force sensor mechanism, the drivecontrol module being operably coupled to output a movement command inresponse to the input received from the force sensor mechanism andinformation received about the configuration of the support structure,the driven wheel being mounted to the base and operably coupled to thedrive control module, and the driven wheel being operable to impartmotion to the base of the cart in response to the movement commandoutput by the drive control module.
 17. The cart of claim 16, wherein:on the condition that the support structure is in the extendedconfiguration, the movement command comprises a first command to controlat least one of velocity or acceleration of the base of the cart withina first range of values; and on the condition that the support structureis in the stowed configuration, the movement command comprises a secondcommand to control the at least one of velocity or acceleration of thebase of the cart within a second range of values different from thefirst range of values.
 18. The cart of claim 17, wherein: the two ormore different configurations comprise a range of partially extendedconfigurations between the stowed configuration and the extendedconfiguration, and on the condition that the support structure is in therange of partially extended configurations, the movement commandcomprises a third command to control the at least one of velocity oracceleration of the base of the cart within a third range of valuesdifferent from the first range of values or the second range of values.